Anode structure for an electron discharge device for ultra high frequencies



July 27, 1948. p CHEVIGNY 2,445,763

. ANODE STRUCTURE FOR AN ELECTRON DISCHARGE DEVICE FOR ULTRA HIGH FREQUENCIES Filed Dec. 24, 1942 INVENTOR P/l UL 6. CHE l/lG/V y BY ATTORNEY Patented July 27, 1948 ANODE STRUCTURE FOR AN ELECTRON DISCHARGE DEVICE FOR ULTRA HIGH FREQUENCIES Paul Georges Chevigny, New York, N. Y., assignor to Federal Telephone and Radio Corporation, Newark,N. J a corporation of Delaware Application December 24, 1942, Serial No. 470,060

4 Claims. 1

This invention relates to improvements in electron discharge devices, and more particularly to vacuum tubes for use at high frequencies.

All vacuum tubes possess certain inter-electrode capacities which, at ultra-high frequencies, in particular, must be taken into careful consideration. In many instances, moreover, the interelectrode capacity of the tube is a limiting factor with regard to the frequencies at which the tube may operate. A convenient type of tube which has been designed and which is now quite widely used for high frequency work is one in which a centrally disposed cathode is surrounded by a concentric grid which, in turn, is surrounded by a ring-shaped anode. The grid connection is in the form of a thin circular disk protruding from the glassenvelope radially of the tube, while the anode lead is in the form of a thicker disk longitudinally spaced from the grid. disk and also extending outwardly through the envelope. The glass envelope is, in this case, preferably sealed to the thick anode disk through the use of suitable annular knife edges. While such tubes provide short leads, important in high frequency work, the question of inter-electrode capacities arises, particularly between the grid and the extension of the anode which leads to the disk, and between the grid and the knife edges.

It is the primary object of the present invention to provide a structure which substantially reduces this interelectrode capacity between the grid and anode.

This invention contemplates a construction by means of which the anode disk is longitudinally displaced relatively to th grid, while the-position of the anode itself about the grid remains the same.

A preferred construction of such a tube is described below and has been illustrated, by way of example, in the accompanying drawings, in which:

Fig. 1 is an elevation, partially in section of a preferred form of vacuum tube in accordance with the present invention; and

Fig. 2 is a partial cross-sectional view illustrating, for the sake of contrast, a construction of a similar tube without the advantages of the present invention.

The vacuum tube illustrated inFig. 1, generally indicated at It], may be of the triode type having a ring-shaped anod l2 concentric with and surrounding an annular grid I4, preferably formed of a plurality of spaced tantalum wires which, in turn, surrounds a cathode in the form of filament I8. The filament H5 may be supplied zso-ms) with power through oppositely spaced leads [8 and central lead 20, extending through and supported by the upper portion of the glass envelope 22. The grid wires M ar preferably supported about their periphery by'a suitable metal cylinder 23 connected to the grid lead in the form of disk 24 extending radially from the tube between the glass envelope sections 22 and 26.

The anode lead is in the form of a thick ring or disk 28 extending radially outwardly from the tube between the glass envelope sections 26 and 3B and sealed thereto by annular knife edges 32 and 34 projectinginto the glass. In order to provide a low resistance path between the anode l2 surrounding the grid [4 and the annular anode lead 28, the two are preferably formed integrally and, in accordance with the present invention, the connection betweenthe anode l2 and the anode lead 28 is effected by means of a reversely curved annular section 36 which longitudinally displaces the anodelead 28 and with it the knife edge32 from the grid l4 and its supporting cylinder 23. The annular section 36 is shaped to have a point of inflection; that is, a change in curvature from concave to convex or conversely depending on the angle at which the tube is considered. By reason of this gooseneck construction it will be noted that the distance between the anode I2 and its ring-shaped lead 28 from the grid I4 and supporting cylinder 23 has been greatly increased in comparison to a structure in which the anode I 2 and its lead 28 are in the same plane. At the same time, the distance from the grid 14 and supporting cylinder 23 from the knife edge 32 has also been increased.

The improvement effective by reason of the present invention can, perhaps, be best realized by comparing the construction illustrated in Fig. 2 with the construction in accordance with the present invention in Fig. 1. In Fig. 2 the anode l2 extends radially outwardly to form the annular anode lead 28'. The connecting portion 36' between the parts [2' and 28 is in relatively close proximity to the grid l4 and its supporting cylinder 23, thus creating a relatively large capacity between these parts, which is the same as increasing the grid-anode capacity. Additionally, in the usual construction shown in Fig. 2 the annular knife edge 32' projecting into the glass envelope section 26 directly surrounds the grid support 23 with a resulting large capacity between these parts, which capacity also increases the effective grid-anode capacity, indicated in Fig. 2 as Cpg.

It will, at once, be clear to thos skilled in this art that the construction illustrated in Fig. 1

effects a reduction not only of the capacity between the grid and the interconnecting section between the portions I2 and 28 of the anode, but also by the longitudinal displacement of the annular knife edge 32 substantially below the grid and supporting cylinder. This capacitative effect has been also substantially eliminated.

While the invention has been illustrated in connection with a certain specific type of tube, it is clear that the principles of this invention are applicable to other types of tubes, in which it is desired to bring out the anode lead substantially radially through the tube envelope. The invention is also obviously applicable to tubes containing more than one grid.

For example, in certain types of tubes it is desirable to extend the grid lead out through the tube at the opposite end from the cathode lead or, in the form shown in Fig. 1 through the bottom of the tube. In such a case, the gooseneck would be reversed and the anode lead 28 would be positioned, above the main anode portion l2 rather than below. In this case, there would result a slight increase in the anode-cathode capacitance but this would be more than offset by the comparative decrease in the anode-grid capacitance.

Accordingly, while I have described above the principles of my invention in connection with the specific type of tube, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as set forth in the objects and in the accompanying claims.

I claim:

1. A vacuum tube, including a cathode, a grid surrounding said cathode, a substantially ringshaped anode surrounding said grid, glass envelope means surrounding'said electrodes, said ring-shaped anode having an integral annular extension protruding outside of said envelope, an annular knife-edge on said extension projecting into and forming a seal with the envelope, and an integral anode section shaped to have a point of inflection connecting the ring-shaped anode with its annular extension and longitudinally displacing'said annular extension and said knifeedge from said grid.

2. A vacuum tube including a cathode, a grid surrounding and concentric with said cathode, a substantially cylindrical support for said grid, a ring-shaped anode surroundin and concentric with said grid, glass envelope means enclosing said electrodes, said ring-shaped anode having an annular extension projecting outside of said envelope, said annular extension being provided with a substantially cylindrical knife-edge coaxial with said grid and grid support and projecting into and forming a seal with said envelope, and an integral anode section shaped to have a point of inflection interconnecting the ring-shaped anode with its annular extension, said anode section longitudinally displacing said anode extension and cylindrical knife-edge away from said grid and grid support.

3. An electron discharge device including, in combination, a centrally positioned cathode, an annular grid surrounding said cathode, a cupshaped anode whose bottom has substantial thickness and is provided with a central opening about the grid and whose rim is provided with an outward lip, an outwardly extending flange integral with the lip of the cup-shaped anode, two annular knife edges integral with said flange, one being positioned on each side of said flange, a first envelope section closing one end of said electron discharge device and sealed to one of said knife edges, and a second envelope section closing the other end of said electron discharge device and sealed to the other annular knife edge.

4. An electron discharge device comprising a a cathode, a grid surrounding said cathode, and a substantially cup-shaped anode provided with an aperture in the bottom portion, said anode being mounted with the walls of said aperture spaced from and immediately surrounding said grid, an envelope surrounding said cathode, grid and anode, a grid disc connected to said grid and sealed through said envelope at a point adjacent said bottom portion of said anode, an anode disc substantially parallel to said grid disc and sealed through said envelope, said anode disc being connected to said cup-shaped anode at a point remote from said bottom portion whereby said anode disc is longitudinally displacedfrom said grid and said disc.

' PAUL GEORGES CHEVIGNY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,091,443 Heintz Aug. 31, 1937 2,228,939 Zottu et a1 Jan. 14, 1941 2,280,980 Samuel Apr, 28, 1942 2,395,043 Goodchild Feb. 19, 1946 FOREIGN PATENTS Number Country Date 464,164 Great Britain Apr. 13, 1937 

